Deck 11: Geologic Time

Question 1

The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal formed by burning of living wood 15,000 years ago. How much of the original carbon-14 would remain today?

A) more than one-half
B) between one-fourth and one-eighth
C) between one-half and one-fourth
D) between one-half and one-third

Answer 1

B

Question 2

Which of the following best characterizes an angular unconformity?

A) Tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity.
B) Horizontal lava flows lie below the unconformity and horizontal, sedimentary strata lie above.
C) The discordant boundary between older strata and an intrusive body of granite.
D) Tilted strata lie below the unconformity with loose, unconsolidated soil above.

Answer 2

A

Question 3

An unconformity is a buried ________.

A) fault or fracture with older rocks above and younger rocks below
B) surface of erosion separating younger strata above from older strata below
C) fault or fracture with younger strata above and older strata below
D) surface of erosion with older strata above and younger strata below

Answer 3

B

Question 4

Which of the following refers to the investigative process by which geologists identify and match sedimentary strata and other rocks of the same ages in different areas?

A) super matching
B) correlation
C) strata indexing
D) cross-access dating

Question 5

Which of the following is an essential characteristic of an index fossil?

A) The organism lived only in specific environments such as beaches or estuaries.
B) The organism only lived for a short period of geologic time.
C) The fossils are exceptionally abundant and well preserved.
D) The fossils occur in deep-water marine sediments, but the organism actually lived in the sunlit, surface layer of the ocean.

Question 6

The era of "ancient life" is the ________ era.

A) Cenozoic
B) Paleozoic
C) Mesozoic
D) Precambrian

Question 7

The subdivision of the geologic time scale that represents the longest time span is called a(n) ________.

A) epoch
B) era
C) period
D) eon

Question 8

The ________ is the idea or concept that ancient life forms succeeded each other in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata?

A) principle of cross correlation
B) law of fossil regression
C) law of correlative indexing
D) principle of fossil succession

Question 9

By applying the law of superposition ________ dates can be determined.

A) conventional
B) radiometric
C) relative
D) both relative and radiometric

Question 10

Which of the following is not a very long-lived, radioactive isotope?

A) U-238
B) K-40
C) Rb-87
D) C-14

Question 11

Who is credited with formulating the doctrine of uniformitarianism?

A) Aristotle
B) Lyell
C) Hutton
D) Playfair

Question 12

About 88 percent of geologic time is represented by the time span called the ________.

A) Paleozoic
B) Precambrian
C) Mesozoic
D) Phanerozoic

Question 13

Consider the names of the eras in the geologic time scale. What is meant by "zoic"?

A) life; living things
B) rocks; lithified strata
C) time; recording of events
D) places; geographic references

Question 14

Which of the following geologic observations would not bear directly on working out the sequence of geologic events in an area?

A) inclusions of sandstone in a granite pluton
B) a well-exposed dike of basalt in sandstone
C) the feldspar and quartz contents of a granite
D) an unconformity between a granite and sandstone

Question 15

Which of the following describes radioactive decay by beta particle emission?

A) The atomic number of the daughter isotope is one more than the parent; the mass numbers are the same.
B) The mass number of the daughter isotope is one more than the parent, and both isotopes have the same atomic number.
C) The daughter isotope has an atomic number two less than the parent and a mass number four less.
D) The daughter isotope has an atomic number one less than the parent and a mass number two less.

Question 16

What is the age of the Earth accepted by most scientists today?

A) 6.4 billion years
B) 4.5 million years
C) 4.5 billion years
D) 6.4 million years

Question 17

The ratio of parent to daughter isotopes in a radioactive decay process is 0.40. How many half-lives have elapsed since the material was 100% parent atoms?

A) less than l
B) more than 3
C) between l and 2
D) between 2 and 3

Question 18

In the late 1700s James Hutton published his important work titled ________.

A) Catastrophism
B) Principles of Geology
C) Modern Earth Science
D) Theory of the Earth

Question 19

Catastrophism ________.

A) was a philosophy that was first expounded by the early Greeks
B) was based upon the belief that Earth was millions of years old
C) helped man understand the true nature of the forces that shaped the Grand Canyon
D) is a modern term used to describe earthquakes and volcanic activity

Question 20

What fundamental concept states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it?

A) law of original correlation
B) theory of correlative deposition
C) law of superposition
D) theory of superstition

Question 21

Who made the first clear statement of the law of superposition? When?

A) John Wesley Powell, nineteenth century
B) William Smith, eighteenth century
C) John Stuart Priestly, nineteenth century
D) Nicolaus Steno, seventeenth century

Question 22

When a radioactive isotope decays by electron capture, the electron ________.

A) combines with a neutron in the nucleus, raising the mass number of the daughter isotope by one
B) combines with a proton in the nucleus; the atomic number of the daughter is one less than the parent
C) makes the parent isotope into an ion with a charge of negative one
D) makes the daughter isotope into an ion with a charge of positive one

Question 23

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
A. Paleozoic B. Mesozoic C. Phanerozoic D. Cenozoic

Question 24

A worm would stand a poor chance of being fossilized because ________.

A) worms have been rare during the geologic past
B) worms have no hard parts
C) worms contain no carbon-14
D) all of these

Question 25

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
A. superposition B. correlation C. original horizontality D. inclusions

Question 26

The era known as the "age of mammals" is the ________.

A) Precambrian
B) Paleozoic
C) Mesozoic
D) Cenozoic

Question 27

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
A. Uranium-238 B. Rubidium-87 C. Carbon-14 D. Potassium-40

Question 28

Visualize five horizontal sedimentary strata exposed in a cliff or canyon wall identified by consecutive numbers, 1 being the lowest bed and 5 being the highest. Which of the following statements concerning the strata are true?

A) Bed 5 is the oldest.
B) Beds l and 3 are older than bed 4.
C) Bed 4 is older than bed 2.
D) Bed 3 is older than beds 2 and 4.

Question 29

Assume that man's recorded history can be stretched back to 4600 years before the present. This is approximately what fraction of geologic time?

A) one ten-thousandth
B) one millionth
C) one billionth
D) one hundred-thousandth

Question 30

The geologic time scale was devised before numerical dating using radioactivity was invented.

Question 31

Which of the following denotes the divisions of the geologic time scale in correct order of decreasing lengths of time beginning with the longest time interval and ending with the shortest?

A) eon, era, epoch, period
B) era, period, epoch, eon
C) eon, epoch, period, era
D) eon, era, period, epoch

Question 32

The term Mesozoic refers to life forms intermediate in complexity between early and much later, more modern-looking life forms.

Question 33

After three half-lives, one-ninth of an original, radioactive parent isotope remains and eight-ninths has decayed into the daughter isotope.

Question 34

Sandstone strata and a mass of granite are observed to be in contact. Which of the following statements is correct geologically?

A) The sandstone is younger if the granite contains sandstone inclusions.
B) The sandstone is younger if it shows evidence of contact metamorphism.
C) The granite is older if the sandstone contains pebbles of the granite.
D) The granite is older if it contains inclusions of sandstone.

Question 35

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
A. electron capture B. alpha emission C. delta capture D. beta emission

Question 36

Assume that you have just examined several flat-lying sedimentary layers. After much study you determine that there is a considerable span of time for which no sedimentary rock layer exists at this site. You have just discovered a(n) ________.

A) angular unconformity
B) series of conformable strata
C) disconformity
D) example of cross-cutting relationships

Question 37

________ is an erosional contact between tilted, older strata below and horizontal, younger strata above.

A) Inverse bedding
B) An angular unconformity
C) A disconformity
D) Cross cutting

Question 38

Numerical age dates based on radioactivity are very important for studying Precambrian geologic history because fossils are rare or absent.

Question 39

Most sedimentary rocks are readily dated by radiometric methods.

Question 40

A disconformity is an erosional unconformity with parallel beds or strata above and below.

Question 41

When a beta particle is emitted, the mass number of the isotope remains unchanged.

Question 42

Rapid burial and possession of hard parts are necessary conditions for the preservation of plant or animal remains as fossils.

Question 43

The Paleozoic is the era of "ancient life."

Question 44

After two half-lives there is no longer any of the original radioactive material remaining.

Question 45

Correlation of rock units between continents or widely separated areas is accomplished by using physical features such as color, texture, and thickness of units.

Question 46

Strata above an angular unconformity were tilted before the older strata were eroded.

Question 47

What are the mass and charge of an alpha particle?

Question 48

The percentage of radioactive atoms that decay during one half-life is always the same.

Question 49

The phrase, "The present is the key to the past," refers to the doctrine of ________.

Question 50

Isotopes of what element are the stable, end products of both uranium decay series?

Question 51

The radioactive isotope, potassium-40, has argon-40 as a daughter product.

Question 52

Radiometric dating means placing events in their proper sequence.

Question 53

The term Paleozoic describes the era of ancient life forms.

Question 54

All of geologic time prior to the beginning of the Paleozoic era is termed the Phanerozoic eon.

Question 55

Phanerozoic, marine, sedimentary strata of the same age on different continents can usually be correlated by their fossil assemblages.

Question 56

What is the inert gas, daughter product of the radioactive isotope, K-40?

Question 57

Pebbles of granite in sandstone and conglomerate resting on the granite suggest that the granite intruded the sedimentary beds.

Question 58

An unconformity involving older metamorphic rocks and younger sedimentary strata is termed a nonconformity.

Question 59

If the ratio of radioactive parent to stable daughter isotope is 1:3, how many half-lives have elapsed?

Question 60

For a radioactive isotope like Uranium-235, what does the 235 indicate?

Question 61

What kind of unconformity is produced when tilted, older strata are eroded and buried by younger strata?

Question 62

On the blank provided beside each geologic cross section below, write the name of the specific type of unconformity that is labeled with an arrow. The v-pattern indicates igneous rocks. All other patterns are different types of sedimentary rocks. (a) ______________________________ (b) ______________________________ (c) ______________________________

Question 63

All of geologic time prior to the beginning of the Paleozoic era is commonly referred to as the ________.

Question 64

What term denotes blocks of older rock enclosed in a body of younger igneous rock?

Question 65

An unconformity in which the strata on either side are essentially parallel is termed a(n) ________.

Question 66

Examine the illustration below (a cross section through the Earth as you might observe on the wall of a quarry or a road cut). Give two reasons why the granite must be older than the sedimentary layers.

Question 67

(a) In the chart of radioactive decay shown below, how many half-lives have elapsed by time (a)?_______________
(b) How many half-lives have elapsed by time (b)? _______________

Question 68

You are asked to interpret the geologic history of a county in California where the geology is quite complex. Aside from visiting various sites in the county for observing geologic sites firsthand, you are permitted to request five different pieces of information or data to aid in your interpretation. List the five that you would choose and explain why each is important for your study.

Question 69

The remains or traces of prehistoric life are called ________.

Question 70

We now live in the ________ era.

Question 71

In an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below. The preceding is a statement of the law of ________.

Question 72

Compare and contrast relative age dating with radiometric age dating. What is a limitation (if any) of each?

Question 73

What general term denotes a buried, erosional surface where rock layers are missing?

Question 74

In a given area where you have little knowledge of the local geology (rocks types, fossils, etc.), what type of unconformity would be the most difficult to recognize in an exposed sequence of rocks? Why?

Question 75

What is the name of a Phanerozoic era that means ancient life?

Question 76

Examine the geologic cross section below. (a) Which feature is the youngest? ______________________________
(b) Which feature is the oldest? ______________________________

Question 77

What process involves identifying and matching rocks of similar ages in different areas?